On Wednesday 19 December 2007 21:02:06 Glauber de Oliveira Costa wrote: > On Dec 19, 2007 12:27 PM, Avi Kivity <[EMAIL PROTECTED]> wrote: > > Ingo Molnar wrote: > > > * Avi Kivity <[EMAIL PROTECTED]> wrote: > > >> Avi Kivity wrote: > > >>> Testing shows wrmsr and rdtsc function normally. > > >>> > > >>> I'll try pinning the vcpus to cpus and see if that helps. > > >> > > >> It does. > > > > > > do we let the guest read the physical CPU's TSC? That would be trouble. > > > > vmx (and svm) allow us to add an offset to the physical tsc. We set it > > on startup to -tsc (so that an rdtsc on boot would return 0), and > > massage it on vcpu migration so that guest rdtsc is monotonic. > > > > The net effect is that tsc on a vcpu can experience large forward jumps > > and changes in rate, but no negative jumps. > > Changes in rate does not sound good. It's possibly what's screwing up > my paravirt clock implementation in smp.
Do you mean in the case of VM migration, or just starting them on a single host? > Since the host updates guest time prior to putting vcpu to run, two > vcpus that start running at different times will have different system > values. > > Now if the vcpu that started running later probes the time first, > we'll se the time going backwards. A constant tsc rate is the only way > around > my limited mind sees around the problem (besides, obviously, _not_ > making the system time per-vcpu). -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
